High reverse breakdown voltage and low on-resistance are required for large current switching elements. To achieve the protection against surge voltage or the like, there has been proposed a structure in which a Schottky barrier diode (SBD) is additionally arranged in parallel between a source and a drain of a power field effect transistor (FET) that functions as a switching element (PTL 1). In a GaN-based semiconductor layer formed on a sapphire substrate, the SBD accompanying the power FET (no specific structure is disclosed in PTL 1) includes an anode electrode that is in Schottky contact with an AlGaN layer and a cathode electrode that is in ohmic contact with a GaN layer, and a two-dimensional electron gas is generated at an interface between the GaN layer and the AlGaN layer.